Add information on version comparison to manpages

Signed-off-by: Dan McGee <dan@archlinux.org>

doc/PKGBUILD.5.txt

@@ -214,7 +214,8 @@ similar to `$_basekernver`.
 		Force the package to be upgraded by a pacman system upgrade
 		operation, even if the version number would normally not trigger
 		such an upgrade. This is useful when the version numbering scheme
-		of a package changes (or is alphanumeric).
+		of a package changes (or is alphanumeric). See linkman:pacman[8] for
+		more infomation on version comparisons.
 
 
 build() Function

doc/pacman.8.txt

@@ -61,7 +61,13 @@ provide the same functionality as foo will be searched for. If any package is
 found, it will be installed.
 +
 You can also use `pacman -Su` to upgrade all packages that are out of date. See
-<<SO,Sync Options>> below.
+<<SO,Sync Options>> below. When upgrading, pacman performs version comparison
+to determine which packages need upgrading. This behavior operates as follows:
+
+  Alphanumeric:
+    1.0 < 1.0a < 1.0alpha < 1.0b < 1.0beta < 1.0p < 1.0pre < 1.0rc
+  Numeric:
+    1 < 1.0 < 1.1 < 1.1.1 < 1.2 < 2.0 < 3.0.0
 
 *-U, \--upgrade*::
 	Upgrade or add a package to the system. Either a URL or file path can be